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TUCoPS :: Radio :: icu2at.txt

Icom IC-u2AT mods

Extended TX mod for the Icom IC-u2AT 
This mod will extend the transmit range of the u2AT from 139 Mhz to
about 161 Mhz (maybe further if you adjust the PLL).  You'll be working
with a surface mount PCB, so you will need a fine point soldering iron
and a very steady hand.  And you will need one diode, like a 1N914, or
a tinyier one if you can get it.
You must have the service manual to help you identify where the new diode is
to go.  Review all the below with the manual before you reach for your
screwdriver and soldering iron!
>remove the battery pack.
>remove 4 screws that hold the sliding guide that the battery pack mounts on.
This is the piece of metal that frames the PL tone switches.
>remove the sliding guide. Be careful that you don't lose the battery release
>there's a screw on the left side of the HT just below the light switch.
Remove it.
>CAREFULLY pry the front panel up.  There's speaker wires AND a flexable lead
that goes to the front panel.  
>There's a shielded PCB that these leads run to.  Carefully pry this up.  It
will then fold down.  There's several flexable leads at the bottom.  
>You should see the CPU now.
With the manual, locate where D113, D119, Q131 are.  
>Where the new diode goes is not marked in the diagram of the CPU PCB.  Locate
the anodes of D119.  This land connects to pin 27 of the CPU chip ic101.
Locate the cathode of D113.  This land connects to pin 20 of the CPU chip.
These diodes are SMDs, and do not look like what you'd expect diodes to look

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